1. Field of the Invention
The present invention relates to the field of heat dissipation, and in particular to a heat dissipation pipe loop and a backlight module using the heat dissipation pipe loop.
2. The Related Arts
Liquid crystal displays (LCDs) have a variety of advantages, such as thin device body, low power consumption, and being free of radiation, and are thus of wide applications. Most of the liquid crystal displays that are currently available in the market are backlighting liquid crystal displays, which comprise a liquid crystal display panel and a backlight module. The operation principle of the liquid crystal display panel is that, with liquid crystal molecules interposed between two parallel glass substrates, a plurality of vertical and horizontal tiny wires is arranged between the two glass substrates and application of electricity is selectively made to control the liquid crystal molecules to change direction in order to refract out light emitting from the backlight module for generating images. Since the liquid crystal display panel itself does not emit light, light must be provided by the backlight module in order to normally display images. Thus, the backlight module is one of the key components of a liquid crystal display. The backlight modules can be classified in two types, namely a side-edge backlight module and a direct backlight module, according to the position where light gets incident. The direct backlight module comprises a light emission source, which is arranged at the backside of the liquid crystal display panel to form a planar light source directly supplied to the liquid crystal display panel. The side-edge backlight module comprises a light emission source, which is arranged at an edge of a backplane to be located rearward of one side of the liquid crystal display panel. The light emitting from the light emission source enters a light guide plate (LGP) through a light incident face at one side of the light guide plate and is projected out of a light exit face of the light guide plate, after being reflected and diffused, to pass through an optic film assembly to form a planar light source for the liquid crystal display panel.
Heretofore, commonly used light emission sources include a cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp (EEFL), and a light-emitting diode (LED), among which the LED is advantageous in respect of environmental conservation and extended life span and is thus widely used. A heat dissipation device that is provided for dissipation of heat from the LED is a vital part for the purposes of preventing the backlight module from getting deteriorated and extending the life span of the backlight module.
In the state of the art, it is common to arrange a heat dissipation pipe loop under a printed circuit board (PCB) on which a plurality of LED lights is mounted in order to achieve heat dissipation of the LED lights.
Referring to FIG. 1, a schematic view is given to show a conventional LED heat dissipation pipe loop, which comprises a liquid pipe 100, an evaporator section 300, a gas pipe 500, and a condenser pipe 700. The heat dissipation pipe loop is filled with a heat dissipation liquid (including water, Freon refrigerant, ammonia, and methanol) that can readily evaporate through absorption of heat. The heat dissipation liquid passes through the liquid pipe 100 into the evaporator section 300 to absorb heat and evaporate into a gas that enters the gas pipe 500 and passes through the condenser pipe 700 to get condensed into liquid for entering the liquid pipe 100 against. This cycle is repeated to enhance the heat dissipation effect.
Further, referring to FIG. 3, the evaporator section 300 comprises an evaporation surface 302, a capillary structure 304, a gas passage 306, a blocking plate 307, a compensation chamber 308, and a liquid phase chamber 309. The heat dissipation pipe loop is an alloy pipe made of metals, such as copper and titanium and a working liquid (including water, Freon refrigerant, ammonia, and methanol) is filled, in a proper amount, into the alloy pipe in a vacuum environment. The working liquid can absorb heat and evaporate into gas.
Referring to FIGS. 2 and 3, an LED module generally comprises LED units 902 and a PCB 904. To achieve heat dissipation, the PCB 904 is positioned on the evaporation surface 302 of the evaporator section 300. The working liquid flows from the liquid pipe 100 into the evaporator section 300 and moves through the liquid phase chamber 309 and the capillary structure 304 in sequence to absorb the heat from an external heat source and convert into gas. The working liquid that has been evaporated into gas passes through the gas passage 306 to flow into the gas pipe 500 to then pass through the condenser pipe 700 for being condensed back into liquid to be cyclically circulated and used in the heat dissipation pipe loop.
It is can be seen from the principle of heat dissipation of the heat dissipation pipe loop that there are both liquid and gas existing in the evaporator section 300. However, it is can be seen from FIG. 3 that the evaporator section 300 of the heat dissipation pipe loop uses the capillary structure 304 and the blocking plate 307 to separate the liquid and the gas from each other. In such a structure, the flow passage of gas is extremely narrow so that the performance of separation of gas and liquid is poor. However, the performance of separation of gas and liquid directly affects the flow speeds of the gas and the liquid and thus affecting the performance of heat dissipation of the heat dissipation pipe loop.